Automatic liquid chlorine dispenser

ABSTRACT

A valve block contains two parallel bores which communicate with a large, vented measuring chamber formed in the block above the bores. At one end the bores are connected, respectively, to a supply of liquid chlorine, and to a swimming pool. A normally closed, spring loaded valve is mounted in each bore intermediate its ends, and has a stem projecting exteriorly of the block for operation by a rotating cam having thereon a detent which momentarily and alternately opens each valve once per revolution of the cam. When one valve is opened, liquid chlorine enters the block to fill the measuring chamber, and when the other valve opens, the contents of the chamber empties into the pool. A cylindrical plunger, which is reciprocably mounted in said block and projects into said measuring chamber, is adjustable to vary the effective volume of the chamber.

United States Patent [72] Inventors Costantinos Pandajis 2,578,215 12/1951 Wilson 222/449 X Rochester; 2,598,583 5/1952 Meyer 222/447 X 2 :4 Helge Primary ExaminerRobert B. Reeves 1 N gzg o Assistant ExaminerFrancis.l. Bartuska I1:511: 3. o. sepazzs, 1969 Attorney-Shlesinger, liitzsimmons & Shle sin ger [45] Patented Aug. 3, 1971 W [73] Assume a I a? Incorporated ABSTRACT: A valve block contains two parallel bores which 0c communicate with a large, vented measuring chamber formed in the block above the bores. At one end the bores are con- [54] AUTOMATIC LlQUm CHLORINE DISPENSER nected, respectively, to a supply of liquid chlorine, and to a 5 claims 3 Driving 58$ swimming pool. A normally closed, spring loaded valve is mounted in each bore intermediate its ends, and has a stem [52] US. Cl 2221438, projecting exteriorly of the block for operation by a rotating ZZZ/442 222,447 222/449 cam having thereon a detent which momentarily and al- [5l] lnt.CL Golf 11/32 temately opens each valve once per revolution f the cam.

[50] Field of Search 222/438, w one valve is opened, liquid chlorine enters the bl k to 250, 434, 380, 484, 442, 70. 44 449 fill the measuring chamber, and when the other valve opens,

the contents of the chamber empties into the pool. A cylindri- [56] Rdennus CM cal plunger, which is reciprocably mounted in said block and UNITED STATES PATENTS projects into said measuring chamber, is adjustable to vary the 2,393,382 1/1946 Kerr 222/135 X effective volume of the chamber,

60 HI I I0 5? 5e s3 62 GI 55 73 1 l 52 58 so 52 47 49 37 4a 45 72 54 4 54 PATENTEUAUG 3m: 3,596,812

SHYET 1 OF 2 INVENTORS COSTANTINOS PANDAMS DAVID e. FLINT BY HELGE K. HEEN ATTOR NEYS AUTOMATIC 'uouin CHLORINE DISPENSER g This invention-relates to liquid dispensers, and more particularly to a device for automatically dispensing a predetermined quantity of chlorine into a swimming pool, or thelike, at predetermined intervals.

For reasonsof health, any. swimming pool of considerable size is usually provided with apparatus forchlorinating the water in the pool. When applied in' proper quantities, the

chlorine kills objectionable bacteria andwill not be han'nful to those swimming in the pooh-1f the ratio of the chlorine to the water in the pool is too low, the pollution count may rise torepair; while the less expensive have been unreliable, or have required periodic manual regulation for satisfactory results:

Moreover, most such prior devices are specifically designed p for chlorinating pools of a given size, and-are not-readily adaptable to chlorinating differently sized pools.

An object of this inventionnisto provide a novel liquid dispenser that is particularly'suited.forperiodically supplying'- a predetermined quantity of chlorine-1o 'the water 'of a swimming pool, or the like;

Another object of this invention is to' providea versatile dispenser of the type described,-which is readily adjustable'tosuit it for use with difl'erently sized swimming'pools.

A further object of this invention-is to provide an improved; device for dispensing fluid chlorine andwhich device is substantially moreinexpen'sive, compact and reliable, than'-prior such devices.

A more specific object of this invention'is to provide'a novel liquid dispenser that is adapted to be gravity fed by a supply of liquid chlorine, and which is operable-automaticallyto dispense a predetermined quantity'of chlorine at 'predeter mined intervals.

Other objects of the invention will be apparent hereinafter from the specification and-fromthe recital of the'appended claims, particularly when read in conjunction with the accom= panying drawings.

ln the-drawings:

I FIG; 1 is a fragmentary'side elevational view of an-auto matic chlorine-dispensing device made'in accordance with I one embodiment of this invention, portions thereof being broken away and shown in section;

parts thereof being broken away and shown in section; and i 45; and 2H0 opposite ends of the block L Projecfing F lG. 3 is a fragmentary sectional view taken along the line 3-3 in FIG. 1 looking in the direction of the arrows;

Referring now to thedrawings by numerals of reference; M)

denotes generally an automatically operated chlorinedispensing device comprising a hollow, rectangular 'metal housing 12 having a cover 14 removably' secured overthe upper end thereof by a plurality of conventional screws 15'.-

Supported by a plurality of annular spacers"'16 on the horizontal bottom wall 17 of housing 12 adjacent'one side thereof -is a large, rectangularmanifold or valve block 18f Block .18 is secured against movement in the housing -12' by a plurality of screws 19, that thread through, thebottom17 dr housing 12 and the spacers 16 into the bottom of block 18! Adjacent itsbottom, block l8has therethrough-a pair 'of 1 spaced, parallel bores 21 and 22; which extend transversely 1 between opposite sides of the block: At one side of block-18' l the bores 21 and22 are counterboredto form in the block-en- FIG. 2 is a fragmentary plan view of-this-device also with and24, respectively; the inner ends of which areconical in configurationuSecured in the outer ends of these ports or chambers'are two annular bushings 25 and 26; Fastened at their inner ends in these bushings to communicate with chambers 23 and 24,-respectively, are two. tubular, elbow-shaped fittings 27 and28, respectively.

Mountedin the chambers 23 and 24 .to'reciprocate into and out of closed'positions in which they seat against the conically shaped inner ends of the chambers, are two, spherical, rubber ballvalves 31 and 32, respectively. Attached to these valves are two, cylindrical 'valve' stems '33 and 34, which project slidablythrough'the-bores 21 and'22 andcoaxially into two, further, enlarged diam'ete'r chambers or counterbores and ,36-formed-in the' opposite side of block 18 coaxially of 'bores 21 and 22,'respectively.

Secured to-theopposite ends of the stems 33 and 34 by cylindrical stem extensions 37 and 38 are two; annular, flexible diaphragms39 and 40, respectively. The outer peripheral edges of these'diaphragms' overlie internal circumferential shoulders 43 and formed around the outer ends of chambers 35 and 36, and "at the inner ends'of the two still further, enlarged-diametercounterbores 45 and 46 formed in block 18 coaxially' of-counterbores 35'and 36, respectively. The'stem -extensions37 and '38 extend slidably through central bores formed in a pairof cylindrical-plugs or diaphragm locks 47 Y and 48, which are threaded into the counterbore's 45 and 46 so that =washers 49 on "their inner 'ends press against the diaphragms 39 and 40 to secure the latter sealinglyagainst the shoulders 43 and. Thediaphragms 39 and 40 thus-provide flexible'seals at the'outer ends of the-chambers 35 and 36'.'

As' shown more" clearly in- FIG; 2, theplugs 47 and '48 projectbeyondtheside of block 18;"and the ste'm'extensions37 and-38 project axiallybeyond their associated plugs 47 and 48.'Each stemextensicm'37 and 38 is surrounded by'a coiled compression spring 50,'which is seated 'at on'eend in"- the'bot-' to'mof anannular' recess 51" formed in the outer end'of each plug" 47 and-'48 'coaxially of itscentral 'bore',-and which is seated at-itsopposite end against a ring'washer 52 thatis secured on the'outer end of each valve extension.'The springs -thus tendconstantly'to urge the ball valves 31 and 32'into theirclosed positions against'the-inner, conical ends of the chambers 23'and24 Fastened'at opposite ends thereof by screws-54 (FIGS. 1

versely'across the outer ends of the'pliigs47 and 48', and in spaced, registering relation to the stem extensions 37 and 38',

is-a rigidj'g enerally U-shaped bracket SSQMounted on this for rotation therewith about an axis positioned midway between the axes of reciprocation of valves 31 and 32'is a circular disc or face cam'57, marginalportions of which are disposed in overlappingregistering relation with the outer ends-of the stem extensions37 and 38 at diame'trally opposite sidesof the camIOn its inner face the cam 57 has adjacent its marginal edge 'a' single camr'nin'g surface or detent 58, which is -,.positioned-to'pass-beneath-the'outer end of each stern extension 37 -and 38 once per revolution of the disc 57.

mam-511s rotated by a conventional timer mechanism 60,-"which-is fastened to the outside of bracket 55, and which has-an output shaft 61 (FIG; 2) that passes through the bracket parallel to shaft 56'. On its'inn'e'rend shaft 61 has secured'thereon a pinion 62, the teeth of which mesh witha gear 63; which is fastened to shaft 56 behind the disc cam 57;

Mounted intermediate its ends for axial sliding movement in a bore 65 (FIG. 1) formed in the forward or left end of the block 18-is a cylindrical plunger- 66. The inner'end'of this I plunger projects into a large, hollow measuring chamber 67,

which is formed in the block- 18aboveand transverse to the valve stems '33, 34, and which opens at its lower end on both of the'charnbers 35 and-36 as illustrated, for example, in FIG.

larged-diameter fluid inlet and outlet ports, or chambers,-23 3. T

bracket, and projecting from the inside face thereof centrally into-the space between the s'tern'extensions 37 and'38 is a rotatable cam-shaft 56; Secured to'the inner end of shaft 56 I Rotatably journaled intermediate its ends in the forward wall of housing 12, and threaded at its inner end into an axial bore 68 formed in the outer end of plunger 66 is an adjusting screw 70. Screw 70 projects beyond the housing 12 and has I fastened to its outer end an enlarged-diameter adjusting knob 72. An elongate screw 73, which is threaded into the periphery of the plunger 66 adjacent the outer end thereof, projects radially from the plunger into engagement with the bottom of the housing 12 adjacent one side thereof to prevent rotation of the plunger 66 upon rotation of the screw 70. Thus, upon rotation of the knob 72 manually in one direction, the screw 70causes the plunger 66 to be advanced, for example, a greater distance into the chamber 67 thereby to reduce the effective volume of the chamber; and upon rotation of the knob 72 in the opposite direction, the inner end of the plunger 66 is retracted, or shifted toward the left in FIG. 1 relative to the chamber 67 to increase its effective volume.

A resilient O-ring 74 (FIG. 1) which is seated in an annular recess in the bore 65 in block 18, surrounds the plunger 66 to seal the outer end of chamber 67, and to prevent its contents from leaking out of the bore 65.

Adjacent its rear or right end (FIG. 1) the chamber 67 is connected by a vertical port or vent 76 with the bore of a conventional elbow fitting 78, which is fastened on the block 18 adjacent its rear edge. The bore of fitting 78 is connected to one end of a length of conventional, flexible tubing 79, which extends through the sidewall of the housing 12 to the exterior thereof.

In use, the housing 12 is fastened in any conventional manner on a support (not illustrated) with its bottom 17 through the bore 22, the outlet chamber 26, and the bore of disposed substantially horizontally. The inlet fitting 27 is connected at its outer end by a length of tubing 80 (FIG. 1) with the bottom of a container or supply S of liquid chlorine, which is positioned above the housing 12, or at least above the block '18, so that the liquid chlorine will be supplied by gravity throughthe tubing 80 to the bore of the inlet fitting 27. Also, the vent tubing 79 is positioned so that it extends at its free end upwardly along the side of the container or supply S of chlorine so that its upper, open end is disposed slightly above the level of the liquid chlorine in the container or supply, when the latter is full. A further length of tubing 82 (FIG. 1) is connected at one end to the outer end of the outlet fitting 28, and extends out of the housing 12 to the swimming pool, or other body'of water that is to be supplied with chlorine. Assuming that the plunger 66 has been previously adjusted into a desired position by its knob 72, the timer unit 60 is energized by inserting the plug 84 (FIG. 1) of its power supply cord 83 into a conventional electrical power supply outlet.

When the timer unit 60 is energized, its output shaft 61 and pinion 62 begin to rotate gear 63, and hence the disc cam 57 about the axis of shaft 56. Assuming at the start that the ball valves 31 and 32 are in their closed positions, and that the cam detent 58 has been rotated past the stem extension 38, and is now approaching the stem extension 37, the measuring chamber 67 will be empty. When the detent 58 passes into engagement with the outer end of the stern extension 37, it forces the extension, and the stem 33 rearwardly against the resistance of spring 50 and the flexible diaphragm 39, thus momentarily unseating or opening the ball valve 31, and permitting liquid chlorine to flow from port 23, through the bore 21 and into the chamber 35. Since the chamber 35 is in communication with the'chamber 67, and through the latter with the chamber 36 and with the vent 76, the incoming chlorine fills chambers 35, 36 and 67, and also tends to rise in the vent 76 and the tubing 79 to a height corresponding to the level of the chlorine in the supply S. At this time the valve 32 is being held in its closed position against the conical end of the outlet chamber 24, so that none of the incoming chlorine can pass through chamber 24 to the bore of the outlet fitting 28.

After the measuring chamber 67 has been filled, the rotating cam disc 57 finally advances the detent 58 from beneath the outer end of the stern extension 37, so that the valve 31 is permitted to return to its closed position. From this point on until the detent 58 has been rotated approximately 180 further about the axis of the shaft 56, the two valves 31 and 32 remain closed. However, after the interval of time it takes to rotate the disc cam 57 one-half a revolution, the detent 58 is finally moved by disc 57 beneath the outer end of the stem extension 38, thereby shifting valve 32 momentarily into its open position as illustrated in FIG. 2. This permits the liquid in the measuring chamber 67, and the slight additional quantity thereof that flows up into the'vent tubing 79, to be discharged the outlet fitting 28 and the tubing 82 to the pool or other body of water that is being chlorinated. In practice, the hous' ing 12 is supported above the level of the water in the pool or other body that is being chlorinated, so that the liquid in the measuring chamber 67 is gravity fed out of the block or manifold 18 to the pool. Shortly after the chamber 67 has been emptied, the disc cam 57 rotates the detent 58 out from beneath the outer end of the stem extension 38; and valve 32 is returned to its closed position by the associated valve spring 50, and the tension in the diaphragm 40.

Thereafter the process continues in a manner that will be apparent from the above description, each valve 31 and 32 being opened alternately, and once per revolution of cam 57.

From-the foregoing, it will be apparent that the instant invention provides a relatively simple, inexpensive and compact device for properly controlling the chlorination of a swimming pool, or the like. The device can be readily adjusted by its plunger 66 to vary the volume of chlorine which will be dispensed with each revolution of cam 57, thereby enabling it to be used for chlorinating differently sized pools. Moreover, the quantity of chlorine dispensed per period of time can be readily adjusted also by adding additional cam detents 58 to the face of cam 57, or by varying the rate of rotation of the cam. This rate can be readily controlled by using a timer unit 66 which is adjustable for this purpose. Also, the two valves 31 and 32 and their associated mountings are similar, so that if desired either can be used as the inlet or outlet valve.

The screw 73 could, if desired, be mounted to extend downwardly through a slot formed in the bottom 17 of housing 12 beneath and parallel to screw 70, so that upon rotation of screw 70, the lower end of screw 73 would slide longitudinally in the slot to prevent rotation of plunger 66 during adjustment of screw 70. Alternatively, screw 73 could be omitted, and the plunger 66 could be provided with a conventional key, which could slide in an axial way or groove in bore 65 of block 18 to perform the same function. Moreover, it will be understood I that the housing 12 could, if necessary, be mounted beneath thelevel of the water in the pool that is to be chlorinated, in which case the output line 82 could be connected, for example, to the suction side of the pump that is used for supplying water to, or recirculating water in, the pool. The pump, instead of gravity alone, would operate to discharge chlorine into the pool upon the opening of valve 32. Furthermore, the dispenser 10 could be used to dispense fluids other than chlorine, if desired.

Having thus described our invention, what we claim is: 1. A device for periodically dispensing predetermined quantities ofliquid, comprising a valve block having therein a vented measuring chamber, and a pair of spaced ports for delivering liquid to and from, respectively, said chamber, a pair of valves mounted in said block between said chamber and said ports, and reciprocable in spaced, parallel paths between open and closed positions to open and close, respectively, said ports relative to said chamber, resilient means normally urging said valves into their closed positions, means for connecting one of said ports to a supply of liquid,

an operating member mounted on said block to rotate about 7 times for each revolution of said member, thereby alternately to deliver liquid from a supply thereof through said one port to said chamber, and from said chamber to the other of said ports, respectively, adjustable means on said block for adjusting the volume of said chamber, thereby to adjust the quantity of liquid delivered to said other port per revolution of said operating member, said block having therethrough two, spaced, parallel bores, each of which has adjacent one end thereof a'first, en-

larged-diameter portion communicating with one of said ports, and adjacent its opposite end a second, enlargeddiameter portion communicating with said measuring chamber,

' said valves comprising a pair of resilient ball valves reciprocable in said first portions of said bores into and out of closed positions in which they seal off said ports from said second portions of said bores, and

a pair of cylindrical valve stems reciprocable in said bores intermediate the ends thereof, said stems being secured at one end to said ball valves, and projecting at their opposite ends coaxially through said second portions of said bores to the exterior of said block,

said resilient means comprising a pair of disc-shaped flexible membranes secured to and surrounding said stems, and secured transversely across said second portions of said bores adjacent the outer ends thereof, thereby to seal said measuring chamber and resiliently to resist movement of the associated valve out of its closed position, and

said operating member being positioned to have said cam means periodically and alternately engage the. outer ends of said stems to shift the latter in a direction to open the associated valves.

2. A device for periodically dispensing predetermined quan-v tities of liquid chlorine from a supply thereof to a swimming pool, or the like, comprising a housing,

a valve block secured in said housing and having therethrough a pair of spaced, parallel bores, each of which is closed at one end, and which communicates adjacent said one end thereof with a vented measuring chamber formed in said block above said bores,

means for selectively connecting said chamber through the opposite ends of said bores to said supply of chlorine and to said pool, respectively,

said means including a pair of normally closed valves' mounted in said bores adjacent said opposite ends thereof, one of said valves being movable to an open position to connect said chamber to said supply, and the other of said valves being movable to an open position to connect said chamber to said pool,

a pair of movable valve stems, each of which is connected at one end to one of said valves and projects at its opposite end exteriorly of said block,

a cam mounted on said block for rotation about an axis extending parallel to an equispaced radially from the axes of said bores, and positioned to engage and move each of said stems in a direction to open its associated valve once per revolution of said cam about its axis of rotation,

means for rotating said cam about the last-named axis,

a plunger slidably mounted intennediate its ends in anopening in said block with the inner end of said plunger projecting into said measuring chamber,

a screw joumaled intermediate its ends in the wall of said housing opposite said plunger, and threaded at its inner end into the outer end of said plunger, said screw being rotatable manually from the exterior of said housing to shift said plunger axially relative to said housing, and

means for preventing rotation of said plunger, whereby upon rotation of said screw the inner end of said plunger is shifted to adjust the effective volume of said measuring chamber,

said block having therein a venting duct which opens at its inner end on the upper end of said chamber, and at its outer end on the upper end of said block,

the outer end of said duct being connected to atmosphere by flexible tubing having an open end positioned above the level of liquid chlorine in said supply, and

said cam being operative alternately and momentarily to engage said stems and to open said valves, so that only one valve is open at a time, whereby when said housing is positioned beneath said supply and above said pool, a predetermined quantity of liquid chlorine will be fed by gravity alternately and successively into said chamber from said supply, and then from said chamber to said pool.

3. A device for periodically dispensing predetermined quantities of liquid chlorine from a supply thereof to a swimming pool, or the like, comprising a housing,

a valve block secured in said housing and having therethrough a pair of spaced, parallel bores, each of which is closed at one end, and which communicates adjacent said one end thereof with a vented measuring chamber formed in said block above said bores,

means for selectively connecting said chamber through the opposite ends of said bores to said supply of chlorine and to said pool, respectively,

said means including a pair of normally closed valves mounted in said bores adjacent said opposite ends thereof, one of said valves being movable to an open posi tion to connect said chamber to said supply, and the other of said valves being movable to an open position to connect said chamber to said pool,

a pair of movable valve stems, each of which is connected at one end to one of said valves and projects at its opposite end exteriorly of said block,

a cam mounted on said block for rotation about an axis extending parallel to and equispaced radially from the axes of said bores, and positioned to engage and move each of said stems in a direction to open its associated valve once per revolution of said cam about its axis of rotation,

means for rotating said cam about the last-named axis,

each of said stems being reciprocable in one of said bores, and the outer ends of said stems normally projecting equidistantly from the same side of said block,

said means for rotating said cam comprising a disc mounted adjacent said outer ends of said stems to rotate about said last-named axis with its face confronting said outer ends, and

said cam comprising a projection on said face of said disc positioned to pass momentarily into operative engagement with one of said outer ends of said stems each of rotation of said disc.

4. A device as defined in claim 3, wherein said valves are a pair of resilient ball valves reciprocable into and out of sealing engagement with a pair of conical valve seats formed in said bores adjacent said opposite ends thereof,

said stems extend from said ball valves slidably through the closed ends of said bores, and

a spring is interposed between said block and each of said stems to urge said stems in a direction to draw said ball valves resiliently and sealingly into engagement with said valve seats.

5. A device as defined in claim 4, wherein a plug is secured in said one end of each of said bores,

said stems extend from said valves slidably through axial bores in said plugs, and

a flexible, annular diaphragm is sealingly secured to each of said stems intermediate its ends to extend transversely across the bore in which its stem reciprocates, and to overlie a circumferential shoulder formed in said block adjacent said one end of each bore, and

each of said plugs at its inner end presses the outer marginal edge of one of said diaphragms sealingly against one of said circumferential shoulders. 

1. A device for periodically dispensing predetermined quantities of liquid, comprising a valve block having therein a vented measuring chamber, and a pair of spaced ports for delivering liquid to and from, respectively, said chamber, a pair of valves mounted in said block between said chamber and said ports, and reciprocable in spaced, parallel paths between open and closed positions to open and close, respectively, said ports relative to said chamber, resilient means normally urging said valves into their closed positions, means for connecting one of said ports to a supply of liquid, an operating member mounted on said block to rotate about an axis parallel to said paths, cam means on said member operative to open each of said valves alternately and momentarily the same number of times for each revolution of said member, thereby alternately to deliver liquid from a supply thereof through said one port to said chamber, and from said chamber to the other of said ports, respectively, adjustable means on said block for adjusting the volume of said chamber, thereby to adjust the quantity of liquid delivered to said other port per revolution of said operating member, said block having therethrough two, spaced, parallel bores, each of which has adjacent one end thereof a first, enlargeddiameter portion communicating with one of said ports, and adjacent its opposite end a second, enlarged-diameter portion communicating with said measuring chamber, said valves comprising a pair of resilient ball valves reciprocable in said first portions of said bores into and out of closed positions in which they seal off said ports from said second portions of said bores, and a pair of cylindrical valve stems reciprocable in said bores intermediate the ends thereof, said stems being secured at one end to said ball valves, and projecting at their opposite ends coaxially through said second portions of said bores to the exterior of said block, said resilient means comprising a pair of disc-shaped flexible membranes secured to and surrounding said stems, and secured transversely across said second portions of said bores adjacent the outer ends thereof, thereby to seal said measuring chamber and resiliently to resist movement of the associated valve out of its closed position, and said operating member being positioned to have said cam means periodically and alternately engage the outer ends of said stems to shift the latter in a direction to open the associated valves.
 2. A device For periodically dispensing predetermined quantities of liquid chlorine from a supply thereof to a swimming pool, or the like, comprising a housing, a valve block secured in said housing and having therethrough a pair of spaced, parallel bores, each of which is closed at one end, and which communicates adjacent said one end thereof with a vented measuring chamber formed in said block above said bores, means for selectively connecting said chamber through the opposite ends of said bores to said supply of chlorine and to said pool, respectively, said means including a pair of normally closed valves mounted in said bores adjacent said opposite ends thereof, one of said valves being movable to an open position to connect said chamber to said supply, and the other of said valves being movable to an open position to connect said chamber to said pool, a pair of movable valve stems, each of which is connected at one end to one of said valves and projects at its opposite end exteriorly of said block, a cam mounted on said block for rotation about an axis extending parallel to an equispaced radially from the axes of said bores, and positioned to engage and move each of said stems in a direction to open its associated valve once per revolution of said cam about its axis of rotation, means for rotating said cam about the last-named axis, a plunger slidably mounted intermediate its ends in an opening in said block with the inner end of said plunger projecting into said measuring chamber, a screw journaled intermediate its ends in the wall of said housing opposite said plunger, and threaded at its inner end into the outer end of said plunger, said screw being rotatable manually from the exterior of said housing to shift said plunger axially relative to said housing, and means for preventing rotation of said plunger, whereby upon rotation of said screw the inner end of said plunger is shifted to adjust the effective volume of said measuring chamber, said block having therein a venting duct which opens at its inner end on the upper end of said chamber, and at its outer end on the upper end of said block, the outer end of said duct being connected to atmosphere by flexible tubing having an open end positioned above the level of liquid chlorine in said supply, and said cam being operative alternately and momentarily to engage said stems and to open said valves, so that only one valve is open at a time, whereby when said housing is positioned beneath said supply and above said pool, a predetermined quantity of liquid chlorine will be fed by gravity alternately and successively into said chamber from said supply, and then from said chamber to said pool.
 3. A device for periodically dispensing predetermined quantities of liquid chlorine from a supply thereof to a swimming pool, or the like, comprising a housing, a valve block secured in said housing and having therethrough a pair of spaced, parallel bores, each of which is closed at one end, and which communicates adjacent said one end thereof with a vented measuring chamber formed in said block above said bores, means for selectively connecting said chamber through the opposite ends of said bores to said supply of chlorine and to said pool, respectively, said means including a pair of normally closed valves mounted in said bores adjacent said opposite ends thereof, one of said valves being movable to an open position to connect said chamber to said supply, and the other of said valves being movable to an open position to connect said chamber to said pool, a pair of movable valve stems, each of which is connected at one end to one of said valves and projects at its opposite end exteriorly of said block, a cam mounted on said block for rotation about an axis extending parallel to and equispaced radially from the axes of said bores, and positioned to engage and move each of said stems in a direction to open its associated valve once per revolution of Said cam about its axis of rotation, means for rotating said cam about the last-named axis, each of said stems being reciprocable in one of said bores, and the outer ends of said stems normally projecting equidistantly from the same side of said block, said means for rotating said cam comprising a disc mounted adjacent said outer ends of said stems to rotate about said last-named axis with its face confronting said outer ends, and said cam comprising a projection on said face of said disc positioned to pass momentarily into operative engagement with one of said outer ends of said stems each 180* of rotation of said disc.
 4. A device as defined in claim 3, wherein said valves are a pair of resilient ball valves reciprocable into and out of sealing engagement with a pair of conical valve seats formed in said bores adjacent said opposite ends thereof, said stems extend from said ball valves slidably through the closed ends of said bores, and a spring is interposed between said block and each of said stems to urge said stems in a direction to draw said ball valves resiliently and sealingly into engagement with said valve seats.
 5. A device as defined in claim 4, wherein a plug is secured in said one end of each of said bores, said stems extend from said valves slidably through axial bores in said plugs, and a flexible, annular diaphragm is sealingly secured to each of said stems intermediate its ends to extend transversely across the bore in which its stem reciprocates, and to overlie a circumferential shoulder formed in said block adjacent said one end of each bore, and each of said plugs at its inner end presses the outer marginal edge of one of said diaphragms sealingly against one of said circumferential shoulders. 